/*
自己选择的路 ,跪着也要走完。朋友们 , 虽然这个世界日益浮躁起来,只
要能够为了当时纯粹的梦想和感动坚持努力下去 , 不管其它人怎么样,我
们也能够保持自己的本色走下去。
To the world , you will be a person , but to a person , you
will be the world .                               ——AKPower
*/
#include <iostream>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <vector>
#include <map>
#include <queue>
#include <cstdio>
#include <string>
#include <stack>
#include <set>
#define IOS ios::sync_with_stdio(false), cin.tie(0)
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
int n;
int a[maxn];
int ans, mx;
int bit[maxn];
int main()
{

    IOS;
    cin >> n;

    ans = 0;
    int flag = 1;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
        if (i > 1 && a[i] != a[i - 1])
            flag = 0;
    }
    if (flag)
    {
        cout << 0;
        return 0;
    }

    //int ct = 0;
    while (1)
    {
        mx = 0;
        memset(bit, 0, sizeof(bit));
        for (int i = 1; i <= n; i++)
        {
            int t = a[i];
            while (t)
            {
                t >>= 1;
                bit[i]++;
            }
            mx = max(bit[i], mx);
        }

        int last = 0, now = 0;
        for (int i = 1; i <= n; i++)
        {
            if (bit[i] == mx)
                last = a[i], now = 0;
            else if (a[i] >= now)
            {
                ans = max(ans, a[i] ^ last);
                now = a[i];
            }
        }

        last = 0, now = 0;
        for (int i = n; i > 0; i--)
        {
            if (bit[i] == mx)
                last = a[i], now = 0;
            else if (a[i] >= now)
            {
                ans = max(ans, a[i] ^ last);
                now = a[i];
            }
        }

        //cout << ct++ << ":" << ans << endl;
        if (ans)
            break;
        for (int i = 1; i <= n; i++)
        {
            a[i] ^= (1 << (bit[i] - 1));
        }
    }

    cout << ans;
    getchar();
    getchar();
    return 0;
}
